Sunday, April 3, 2011

You make my drive hard when you allocate my clusters

Without this rectangular block filled with platters, actuator arms and read/write heads you would not be able to permanently store anything to your machine.

I talked about bits, bytes kilobytes and all the other bytes in my first blog. Well, that knowledge will come in handy when discussing hard drives.

To me, the hard drive is not as complicated as other devices such as the CPU or RAM.

First, let's talk about how the data is actually stored. As you can see in the above picture, there are silver disks on the inside of the drive. These disks are called platters. The platters are where the actual data is stored. A platter is made mostly of aluminum but is coated with a polished magnetic oxide (it looks like a shaded mirror).

The magnetic oxide is where the actual data is stored. At the end of the actuator arm is a read/write head. The read/write heads hover extremely close to the platters (nanometers; we're talking microscopically close). When data is written, the actuator arm moves the read/write heads outward from the center of the platter while the drive spins. The movement of the actuator arm is the faint clicking noise that you sometimes hear coming from your computer (save a word document and listen for it). This may sound like a slow process, but the platters actually spin extremely quickly. A hard drive can spin anywhere from 4200 revolutions per minute (RPM) to 15,000 RPM.

I hope you paid attention to my first blog because here is where bits come into play. When data is written, the read/write head converts electricity into a magnetic field which alters the bit region on the platters by changing the flux pattern to [N-S] or north-south. When data is read the read/write head moves over the bit region and reads the flux pattern. If the head reads [N-S] it returns a bit value of 1; if it reads [S-N] it returns a bit value of 0.

In a future blog we will discuss sectors, clusters and tracks and how they relate to this blog.